Inspiron 580, recommended PSU replacement?

580S only takes dell proprietary unit.

580 Mini Tower can use EVGA 700BR.

https://www.bestbuy.com/site/evga-700w-atx12v-eps12v-80-plus-bronze-power-supply-dc-dc-technology-black/6346160.p?skuId=6346160

The overall power rating is not the issue.  It must be EPS12v and 80 percent efficient.

It must also have 150W combined for the 3.3v/5v rails.   Smaller units will only have 90 to 130W at 15 or 20A on those rails.  25A is needed.

Power supplies are not a single spec of watts.  

This is why EVGA 750B1 works fine but the B2 BQ N1 W1 versions of the same vendor DO NOT WORK correctly.

Dell 305W  460W  525W 875W etc all meet this spec or better.

https://www.dell.com/community/Desktops-General-Read-Only/XPS-8700-Power-Supply-Replacement/td-p/4567328

Thats why even corsair CX500 is not sufficient.   5vSB should be 4 amps and the 3.3v/5v rails should say 25 amps.

While impressive, I don’t need that powerful of a power supply.

Dell power supplies down to 305w have 142 TO 150 WATTS combined for the 3.3V/5V RAILS at 25 amps OR MORE.   5V standby is 4 amps or more.

For the Dell 875w unit this goes UP to 225w combined and 30 amps.

Each vendor decides how much or how little is needed for each rail.

HOWEVER you cannot get MAX amps for all rails at the same time.

Power Supplies are not a Single voltage and a Single Spec of Watts.

Even the 460W dell has 142W to 150W or more on the 3.3v /5v rails combined and 25 AMPS on 5v.  This is the case all the way down to 305W units. On the Dell 875W unit this goes up to 225W combined with 32A on 5v rails.

This is why EVGA SUPER NOVA 750B (120-PB-0750-KR)

EVGA 700BR is as low as you can go.

https://www.bestbuy.com/site/evga-700w-atx12v-eps12v-80-plus-bronze-power-supply-dc-dc-technology-black/6346160.p?skuId=6346160

works fine but the B2 BQ G2 750W models from the SAME VENDOR do not work correctly.

https://www.amazon.com/dp/B00K85X23O/

DELL 460W

Note the 150w even on the dell 305w power supply.  The 875w unit has 32 amps on 5V and 30 amps on 3.3V

DELL 305W

DELL 875W

Can I use a 165mm power supply to replace the stock 140mm unit in the Dell Inspiron 580?

The Bestic power supply in my Inspiron 580 delivers 160 watts on the 3.3 and 5v rails combined, 300 watts total.  Dell designed the 580 with space and connections for 2 optical drives, 2 hard drives, six USB connections and 4 DIMM slots that all need 5 volts or lower.  The PCIe slots are supposed to be able to run at 3.3v if needed as well.  

The motherboard should have a voltage regulator that could convert 12v to the lower voltages required.  However, the greater the difference in the input and output voltages, the more the regulator will be stressed.  I'd bet that Dell designed the power supply specs with 150+Watts combined on the 3.3 and 5 volt rails to minimize the stress on the regulator and extend the life of the regulator/motherboard.  Mine is still going strong.

While I've modified my 580 outside specs with an i7-870 (also Xeon 3480), SATA SSD and 32GB of low-density 2Rx8 RAM, I don't think I'd try using a power supply that substantially under-delivered power on the 3.3 and 5v rails.  It's hard to know the long-term impact but it likely wouldn't be good.

I am going to replace the power supply and found very few choices that met or exceeded the 160 combined 3.3/5v wattage spec.  The EVGA 700 BR mentioned by speedstep is 140mm in depth - the same as the stock Bestic in my unit.  It offers 150w combined 3.3/5v, 20A 5v and 24A 3.3v.  Close to the original spec.  It's the only new 140mm power supply that I've seen that comes close to matching the specs on my original Bestic.  I've checked all the Corsair, EVGA and several other models...all are 130W combined or lower.

I was wondering if I could use a longer power supply than 140mm.  This would open up a few more options including the older EVGA supernova 120-PB-0750-KR mentioned by speedstep that is at least 160mm.  The newer EVGA 850BQ that offers 160 combined watts on 3.3/5volt rails with 25A on each but is also 25mm longer than the 140mm stock unit. 

Inside and along the top of the case, there appears to be a very short metal "stop" at 140mm that the existing power supply rests against.  If that stop isn't movable then a longer replacement power supply would rest on top of it rather than snugged up against it.  I could see this creating fit and grounding issues and was wondering if it is realistic to use longer power supplies without modifying the chassis.

it's not about wattage, ras951 - it's about amperage

what speedstep said is true!

My relative's Dell Inspiron 580 which we bought back in April 2011 is still working well in 2020, even with the stock PSU it came with

after more than 3 years after I made that post, the stock power supply in that Inspiron 580 mid tower desktop PC gave out in late October 2023 and would no longer power on the computer anymore.  I opened up the pc case and found out the stock PSU was a Bestec atx0300d5wb (some of the older model Bestec PSUs many years ago were known for being "gutless wonders").  so I quickly ordered & replaced that Bestec power supply with a Dell D300ND-00 (dp/n 0K67CY) power supply and my relative's Inspiron 580 computer powers on & works again.